Night time cooling pad operation during extremely hot weather

Recently, a large region in the Midwest of the USA experienced extremely hot weather. As a result, many producers were facing severe losses because large numbers of birds died. In certain situations this could have been avoided if proper cooling regimes were applied. One such a measure is turning on the pad coolers at the right time, specifically at night, and this should be based on the inside temperature of the house.

It is generally recommended that evaporative cooling pads should not be operated at night because the relative humidity of the air outside a poultry house tends to run 80% or higher at night. Operating pads when the outside relative humidity is above 80% produces little cooling and tends to saturate the income air with moisture making it more difficult for the birds to cool themselves.

Outside air temperature and relative humidity are inversely related. This means that as outside temperature rises in the morning, the relative humidity decreases. Conversely, when air temperature in the evening falls, the relative humidity of the air increases. As a result, poultry producers will find that in the morning when temperatures climb above 80oF, the relative humidity will fall below 80 % and their evaporative cooling systems are able to produce a significant amount of cooling without saturating the incoming air with moisture. In the evening when the outside temperature falls below 80oF, the humidity increases above 80%, and the cooling produced by an evaporative cooling system becomes very limited.

The keys to effective evaporative cooling pad operation is not necessarily placing them on a time clock so they can’t operate at night but rather setting them to operate at a proper temperature. Evaporative cooling pads should be set to turn on somewhere in the low to mid eighties with older birds, not in the seventies. Setting pads to operate in the high seventies will allow the pads to operate in situations where very little cooling would be produced and they would tend to increase the incoming relative humidity to 90% or higher. Setting pads to operate in the low to mid eighties will insure that the cooling produced through air movement is maximised while causing the pads to shut off at night during normal hot weather and to continue to operate into the late evening during periods of extreme weather.